论文部分内容阅读
It has recently been reported that Li+ doping can result in the enhancement of upconversion (UC) emission.It is suggested that the improved UC intensity originates from two mechanisms: the break of local crystal field symmetry around rare-earth ion and the reduced number of OH-groups.That is to say, the introduction of Li+ not only increases the radiative transition rate but also decreases the nonradiative relaxation rate.